1. Field of the Invention
The present invention relates to a safety door device provided on a mold clamping unit of an injection molding machine.
2. Description of the Related Art
In an injection molding machine, a clamping unit moves a movable mold mounted on a movable platen against a stationary mold mounted on a stationary platen, closes the molds, and injects resin into the molds, after which the clamping unit is moved, the molds opened, and the molded article removed. When mounting the molds on the clamping unit, when performing maintenance on the clamping unit, and further, when removing the molded article manually, it is necessary to be able to access the clamping unit from the outside. However, since the clamping unit is designed to open and close the molds, there is a risk of an operator getting a hand caught in the molds. Accordingly, as a precaution a safety door is provide on the clamping unit and configured in such a way that the clamping unit can only move when the safety door has closed the clamping unit.
Usually, a safety door is provided on both a front side, that is, an operation side where an operator mainly operates, and a rear side opposite the front side of the clamping unit. In order to ensure safety, it is necessary to provide switches that detect opening and closing of the safety doors on both the operation side safety door and the safety door on the side opposite the operation side. In order to prevent an increase in cost brought about by providing detection switches for each of the safety doors, some injection molding machines integrate the operation side safety door and the safety door on the side opposite the operation side into a single body, thus reducing the number of detection switches. However, such a single body structure increases the mass of the safety door, which is undesirable in that the safety door is opened and closed repeatedly when removing molded articles from the mold manually and thus imposes an undue burden on the operator.
Consequently, in an attempt to provide safety while at the same time reducing the burden on the operator, safety doors in which the operation side safety door can be opened and closed independently of the rear door are known.
For example, a safety door construction is known in which a rotary shaft is provided between the operation side safety door and the safety door on the side opposite the operation side, such that, when the operation side safety door is locked, the rotary shaft cannot rotate and thus the safety door on the side opposite the operation side cannot be opened. When the operation side safety door is not locked, the operation side safety door can be freely opened and closed. However, when the safety door on the side opposite the operation side is opened, the rotary shaft rotates, opening the operation side safety door a predetermined distance only, and when the safety door on the side opposite the operation side is open the operation side safety door is always open, and further, only when the safety door on the side opposite the operation side is closed can the operation side safety door be completely closed (see, for example, JP2002-187184A).
Moreover, a safety door construction is also known in which brackets are projected from each of the operation side safety door and the safety door on the side opposite the operation side, respectively, the bracket from the safety door on the side opposite the operation side is disposed rearward of the bracket of the operation side safety door (on a side at which the door closes), such that, when the operation side safety door is closed the safety door on the side opposite the operation side also closes. The operation side safety door can be opened independently, but when the safety door on the side opposite the operation side is opened the operation side safety door also opens order to ensure safety (see JP55-58321U).
Further, an invention in which a coupling mechanism that links the operation side safety door and the safety door on the side opposite the operation side together manually, such that when the operation side safety door and the safety door on the side opposite the operation side are coupled by the coupling mechanism both safety doors move together, and when the coupling is released both doors can be freely opened and closed independently, is also known (JP64-36425A).
Arrangements in which, in an injection molding machine having a operation side safety door and a safety door on the side opposite the operation side, when the operation side safety door can be freely opened and closed independently, and further, when the operation side safety door is shut, the safety door on the side opposite the operation side also is always shut as well in order to provide safety, and at the same time reduce the burden on the operator, are well known as described above. However, there are drawbacks to the above-described approaches.
For example, in the invention described in JP2002-187184A, even when the safety door on the side opposite the operation side is wide open, because the angle of the rotary shaft does not increase beyond a certain angle, the operation side safety door does not open further than that angle, and moreover, even when the safety door on the side opposite the operation side is closed, the operation side safety door cannot be closed.
In addition, in the invention described in JP55-58321U, when the safety door on the side opposite the operation side is opened and the safety door on the side opposite the operation side stopped after bracket impact, even though the motion of the safety door on the side opposite the operation side is stopped the operation side safety door continues to move by inertia, such that the operation side safety door is an in uncontrolled state, and consequently, safety cannot be achieved.
In the invention described in JP64-36425A, if the operation side safety door and the safety door on the side opposite the operation side are linked by the coupling mechanism, both safety doors move as a single body, and consequently, safety can be achieved without entering an uncontrolled state. Further, if the coupling is released, both safety doors can each be opened and closed independently, thus reducing the burden on the operator. However, the coupling mechanism must be operated manually, and further, since the structure is such that both safety doors can open and close separately, it is necessary to provide detection switches to detect opening and closing of both safety doors in order to provide safety, which increases costs.